A solution can be reached by considering the impact of a 1 at r6 c1.
immediately r6c6 becomes 7, r4 c4 becomes 8 and r5c5 9
now r5c1 is 8 and we have 89 in rows 4 and 5 as well as 89 in col7 all pressurising r6c9 to hold both 8 and 9 which it can't do

Hence 1 must lie ar r3c1 ...and so on.. to the solution.

So knowing that Sudoku pro's hate forcing functions, can anyone offer me the name and logic behind the solution you would use!!!!
Note : I have removed an 8 in r2c2 that was not apparent at the crunch point!

Last edited by George Woods on Mon Aug 14, 2006 11:56 pm; edited 1 time in total

Sorry for wating your time maybe-- I made an error in my posting -- the 8 in box1 should not be there (although curiously this 8 appears in the same place with either position of the 1 in col 1) - SO IS THIS A CLUE TO THE PROPER TECHNIQUE FOR SOLVING THIS ONE?

The solution as you point out is so easy that I thought "It can't be!" So to make sure I had recorded the crunch point correctly, I went back to the original puzzle and repeated the solution from scratch to the crunch point and guess what ANOTHER STUPID ERROR IS REVEALED ON MY PART -- the 2 in box 4 should not be there !!!!!!!!!!!

Once again we find, unlikely though it seems, that the key lies in the least populated row,column, or box. I suppose seeing the very obvious 35 and 34 in the row should have prompted the though "Bet there is a 45 along here" - but it's so easy to see it after the event!!!!